This proposal focuses on energy metabolism in two preparations, a hepatoma cell line (HTC cells), and an isolated hepatocyte preparation. The investigation will utilize equations to quantitate the relative flux of carbon through TCA cycle related pathways. These equations were derived by the P.I. in the process of developing a new steady state model of TCA cycle carbon isotope distribution. The unique feature of these equations is that they capture information about the pattern of energy metabolism not available using other techniques. A key metabolic distinction between hepatocytes and hepatoma cells is the use of glutamine as a significant energy source by tumor cells. Thus, the major goal of the hepatoma metabolic studies is a quantitative analysis of the pattern of glutamine metabolism. In comparing the pattern of metabolism in hepatoma and hepatocytes, modeling techniques developed by the P.I. will be used which consider the possible existence of more than one pool of specific metabolites. The major goal of studies focusing on hepatocyte metabolism is to improve the procedure for carbon isotopic measurement of gluconeogenesis. The P.I. has examined the mathematical basis of a commonly used correction factor for isotope dilution in gluconeogenesis ("Hetenyi's factor") and has determined that it may yield misleading estimates of gluconeogenesis in some instances. Thus, a new protocol will be developed to estimate the dilution in the specific radioactivity as extracellular alanine is converted to the oxaloacetate pool which is the precursor for glucose. The long term goals of this project are to understand the quantitative role of factors which direct the flux of metabolites into either biosynthetic or oxidative pathways and to quantify metabolic differences between normal and transformed cells.